Injection devices, such as the Owen Mumford Autopen®, are commonly used by patients to self-administer injections of medicament. Such devices are typically provided in a pen-like body which contains a cartridge of medicament (it will be appreciated that the cartridge may, for example, comprise a syringe and may be received within or defined by the injector housing depending on the particular device configuration; as such references herein to a “cartridge” will be interpreted accordingly). The injection device generally comprises a delivery mechanism which is arranged to dispense the medicament via a needle in response to a user pressing a button or trigger. Depending upon the type of device and or medicament to be delivered the injection device may be arranged to deliver the entire contents of the cartridge or a selected dose therefrom (and in the latter case the injector may also include a dose selection device). In some injection devices the delivery mechanism may also be arranged to move the needle between a retracted and delivery position and, in doing so, may automatically pierce the skin of the user prior to the dispensing of the medicament.
It is a common requirement that injection devices signal to the user when the injection is complete. The term ‘injection complete’ is used to refer to a condition in which a satisfactory delivery of the drug has been achieved. Such an indication may be one or more of a visual, audible or tactile indication.
One such arrangement has been provided in the applicant's earlier International Patent Application WO2009/141650 in which an injection device is provided with a magnetically-operated indicator for generating an injection complete indication.
A further injection device is disclosed in WO2006/134153, in which an injection pen is provided with a plurality of sensors that sense when a user is taking a specific action with the device and a sound generator to generate a signal corresponding to the action being taken.